Islet neogenesis associated protein (INGAP) is a product of a gene expressed in regenerating hamster pancreas. INGAP gene is expressed in acinar cells, but not in islets. Western blot analysis demonstrates the presence of INGAP in Ilotropin, a protein extract isolated from cellophane wrapped pancreata, but not in extracts from control pancreata. A synthetic pentadecapeptide, corresponding to a region unique to INGAP, stimulates a 2.4-fold increase in [3H]thymidine incorporation into hamster duct epithelium in primary culture and a rat pancreatic duct cell line but has no effect on a hamster insulinoma tumor cell line. A portion of human INGAP gene has been cloned and appears to be highly homologous to the hamster gene. INGAP gene is a pancreatic gene expressed during islet neogenesis whose protein product is a constituent of Ilotropin and is capable of initiating duct cell proliferation, a prerequisite for islet neogenesis. J Clin Invest 1997 May 1; 99(9):2100-9. There is a need in the art for tools for measuring INGAP to enable and facilitate the full exploitation of this important protein for fighting human disease, such as diabetes types I and II.